This isn't actually homework but it might as well be. I think the resistors are in parallel and therefore are equivalent to 235 ohm resistance. Could someone please confirm or refute? Thanks.
Are these resistors in parallel?
- Thread starter seanspotatobusiness
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Thanks!
Yes they are. I can supply an example where it will be almost impossible to tell.This isn't actually homework but it might as well be. I think the resistors are in parallel and therefore are equivalent to 235 ohm resistance. Could someone please confirm or refute? Thanks.
While this is sufficient for them to be in parallel, it is not necessary.
They are also in parallel if node 1A is connected to node 2B and node 1B is connected to node 2A.
The bottom line is that two (two-terminal) devices are in parallel if whatever (symbolic) voltage appears across one also must appear across the other.
Is it easier to determine with the schematic redrawn?
BTW, not advisable to connect LEDs that way. One of the LEDs will hog current.
Hi,Yes they are. I can supply an example where it will be almost impossible to tell.
Where is this said example, i'd like to see it ?
Sounds like a test question to share shamelessly.Yes they are. I can supply an example where it will be almost impossible to tell.
Hi,Sounds like a test question to share shamelessly.
Well i saw one example one time where there were just two resistors and the question was are they in series or in parallel. There was nothing else to the circuit, just those two resistors.
So the answer is, "Yes."
There's nothing that says that being in series and being in parallel are mutually exclusive.
Hi,
Well a battery in series with two resistors in series cant be a parallel circuit right?
Did you mean 'always' mutually exclusive, or did you mean from the viewpoint of the observer ?
Pick any two of the three nodes in the circuit you describe and place the components along each possible path in a separate black box. You now have a set of black boxes each connected to the same two nodes, thus they have the same (symbolic) voltage across them at all times. This is the definition of components in parallel.
The term "mutually exclusive" means that if one case is true, that the other cannot be true. Note that it does allow for both cases being false. Logically it is the same function as a NAND gate.
This is absolutely true. It can only be defined in terms of an outside voltage (or current) source.
It gets interestinger, too, when you start working with LC tank circuits. There is really no difference between a series and a parallel resonant circuit....the CIRCULATING current is maximum at resonance in either case. But, how they respond to external stimuli is quite different. This is why the Loaded and Unloaded Q of a tank circuit can be two very different figures.
Stay TUNED!
Eric
Would you agree that A and B are in parallel?
Would you agree that the middle circuit is the circuit you described (a battery in series with two resistors in series)?
Would you agree that the bottom circuit is still the same circuit?
I would agree also that is drawn in what we call in Spanish a (capciosa) way Not sure if you would translate as deceitful.
How is it deceitful? Deception is used to convince you of something that is not true.
I agree that it is drawn in a way that forces us to consider things we normally don't consider, but none-the-less it is drawn in a way that clearly demonstrates that you can pick any two of the three items and properly say that the series combination of those two items is in parallel with the third.
I agree that it is drawn in a way that forces us to consider things we normally don't consider, but none-the-less it is drawn in a way that clearly demonstrates that you can pick any two of the three items and properly say that the series combination of those two items is in parallel with the third.
Hi,
Well what you are drawing there looks like you are talking about the 'viewpoint' as i was thinking you might be talking about. That is where we allow the author to define how we view the circuit. But i dont think that's the right view for this subject area because we already have defined 'series' and 'parallel' and i dont think our aim should be to mix the two up so that we no longer have a distinction.
For example, if you tell someone to connect two LEDs in parallel, that's a lot different than if you tell them to connect two in series, and if you tell them to connect three LEDs in parallel, that clearly not the same as if you tell them to connect three in series. Which brings us to a useful definition if we examine the voltage across those LEDs.
In the parallel case, the voltage is the same for each and every LED, and nowhere do we measure a higher voltage. When we measure the voltage for each LED in the series case, we measure the same for each LED but other voltages in the circuit can be found to be higher such as across two of the LEDs. The sum of the voltage drops in a series circuit is zero. Measuring from one chosen terminal, each other terminal voltage will be different in a series circuit while in a parallel circuit the voltage will be the same for every terminal that is not the reference terminal.
Also, duality depends on defining series as different than parallel, and the formula for the total resistance of two resistors in series is different than for two resistors in parallel.
But my main point here is that if we find a way to confuse series with parallel then we've lost something in the process not gained something, and then we find it harder to talk about circuits that are series and parallel.
Hopefully i understood what you were saying there though
One other little point is that two resistors in parallel can never be used in a circuit with another third resistor to form a series only circuit, that is where all three are in series, while two resistors in series can be used with a third resistor to form a circuit with three resistors in series. That means there must be a difference between two resistors connected with only one node in common (three nodes total) and two connected with each of both terminals connected together forming only two nodes.
Note that a string of LEDs may have the same numerical voltage across them (though we have to assume they are absolutely, perfectly, identical to make this claim) but each is a different symbolic voltages.
I never said that there was no distinction between series and parallel. As you say, we have definitions for each of them.
Two components are in parallel if they have the same symbolic voltage appearing across them.
Two components are in series if they have the same symbolic current flowing through them.
What you are trying to do is to place caveats on these definitions so that you can claim that two components that satisfy the definition for being in parallel somehow aren't in parallel and the same for series. Well, at the very least that buys you the burden of supplementing the definitions with the caveats you want to insist upon.
I never said that there was no distinction between series and parallel. As you say, we have definitions for each of them.
Two components are in parallel if they have the same symbolic voltage appearing across them.
Two components are in series if they have the same symbolic current flowing through them.
What you are trying to do is to place caveats on these definitions so that you can claim that two components that satisfy the definition for being in parallel somehow aren't in parallel and the same for series. Well, at the very least that buys you the burden of supplementing the definitions with the caveats you want to insist upon.
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